Core construction for magnetic circuits



Aug. 23, 1932.

R. E. STEWART CORE CONSTRUCTION FOR MAGNETIC CIRCUITS Filed April 5,1929 2 k2. Stew rt Willa/u Patented Aug. 23, 1932 UNITED STATES PATENTOFFICE RALPH E. STEWART, OF LOS ANGELES, CALIFORNIA, ASSIGNOR OFONE-HALF TO CHARLES RUESS, OF LOS ANGELES, CALIFORNIA 003 CONSTRUCTIONFOR MAGNETIC means Application filed April 3,

This invention relates to core constructions for magnetic circuits andto a construction which will prevent the crowding of magnetic flux in anelectromagnetic construction wherein there is a primary winding and asecondary winding which are movable relatively to each other.

Anobject of the invention is to provide an improved laminatedconstruction adaptedto be used in magnetic circuits which are energizedby either an alternating current or a pulsating direct current.Heretofore it has bcen'customary to form laminated members in magneticcircuits which are energized by either alternating or pulsating directcurrents by firmly and rigidly fastening the laminations together. Ifthe laminated member or core is to come in contact with another memberin the magnetic circuit a great deal of care involving time and expenseis usually taken to mill off the abutting or engaging surfaces betweenthe two members. An attempt is made to have the abutting surfaces assmooth and as exact as possible to allow the two members to fit closelytogether in an endeavor to prevent the creation of noise by thelaminated member vibrating due to the changes in the magnetic flux.

It is an object of the present invention to provide an improvedlaminated construction which is so constructed that it will not producethe objectionable noise. It is usually found that regardless of the caretaken in milling off the abutting surfaces between two members in amagnetic circuit that these two members vibrate under the influence ofchanges in the magnetic flux producing an objectionable noise and theimproved con struction is highly advantageous in that the noise ispractically completely eliminated.

It is another objectof the invention to provide an improved laminatedconstruction to be used in magnetic circuits which will not onlyeliminate the objectionable noise but which will dispense with theexpensive milling operations heretofore believed to be necessary in theconstruction of the laminated member.

The invention is highly useful when applied to a device such as avoltage regulator 1929. Serial No. 352,261.

in which there is a primary coil and a secondthe magnetic flux generatedby the primary coil. This magnetic flux generated by the secondary coilin opposition to the primary coil or winding tends to crowd the flux ofthe primary winding away from the secondary coil. As a result of this itwill be found that a curve representing the magnitudes of voltages orcurrents induced in the secondary winding is very peaked, instead ofapproaching a smooth curve similar to'a sine curve. This nature of theinduced currents in the secondary winding is disadvantageous and it isanother object of the invention to provide a construction onanelectromagnetic device which will prevent or resist the crowding ofthe flux generated by the primary winding so that the induced currentsin the secondview which will be made manifest in the following detaileddescription and specifically pointed out in the appended claimsreference is had to the accompanying drawing for an illustrativeembodiment of the invention wherein:

Fig.1 is a perspective view of a voltage regulator to which theinvention has been embodied.

Fig. 2 is a longitudinal vertical section taken through the same.

Fig. 3 is a vertical section taken substantially upon the line 33 uponFig. 2.

Referring to the accompanying drawing for an illustrative embodiment ofthe invention it will be understood that the invention may be applied toany magnetic circuit under a variety of different circumstances.However, the invention haspractically no application to anelectromagnetic circuit created by or energized by a direct current andtherefore the invention is limited in its-application to a magneticcircuit which is energized by either an alternating current or apulsating direct current. The invention 'is illustrated as havingbeenapplied to a voltage regulator comprisin a lower rectangular frame part10 whic has two upstanding posts 11 and 12 at its opposite endsconnected by a guide 13. Transverse supporting members 14, 15 and 16extend across the frame and serve to support the lower set oflaminations forming the lower core 18. The lower set of laminations areloose, i. e. they are merely resting on the transverse supportingmembers 14, 15 and'16. They are not otherwise connected to each otherand are merely held side by side by the sides of the lower frame part.Minute spaces are between the laminations, such spaces being representedby the relatively heavy lines on the drawing. By virtue of the fact thatthe laminations do not completely fill the frame between its side walls19 and 20 each lamination is ca pable of moving slightly or vibratingindependently of the others. Each lamination of the lower core has arecess '21 formed there .movable relatively to each other. Thetransverse members 24, 25 and 26 extend between the sides 27 and 28 ofan upper movable frame,

the sides being connected by a back wall 29 which has an actuating screw30 threadedly connected thereto. The actuating screw 30 is adapted to berotated by a crank 31 which is journaled in the back wall of the lowerframe 10. By rotation of the crank 31 the upper frame and the upper setof laminations, together with the upper coil 32 constituting thesecondary winding can be adjusted with respectvto the lower set oflaminations and the lower coil, the movement of the upper frame beingguided by the guide 13. The voltage regulator is shown in Fig. 2 asbeing in approximately no-load position or in that position whereinlittle if any current is being induced in a secondary winding.

In the lower set of laminations 18 there are formed apertures 33 and intheir top edges there are formed recesses 34. These apertures andrecesses are adapted to receive copper bars 35 and 36 which extendtransversely across the lower core. These copper bars extend through thesides 19 and 20 of the lower frame and are welded, brazed, or otherwisesecured to copper plates 37 and 38 which are arranged on the outer sidesof the side walls 19 and 20 within the sides of the primary coil 22. Inthis manner the bars 35 and 36 together with the blades 37 and 38 form aplurality of short circuited coils in the lower core, the axes ,of whichare arranged at right angles to the axis of the primary winding 22 andparallel to the direction of movement of the secondary coil 32. o

The voltage regulator is adapted to be energized by either analternating current or a pulsating direct current and a feature of theimproved construction resides in the fact that the improved voltageregulator is practically noiseless. Each lamination being loose, canvibrate independently of the others due to the changes or variations inthe magnetic flux. The theory of the improved construction is asfollows:

When the laminations are all rigidly fastened together as in priorconstructions and the abutting surfaces between the upper and lowercores are carefully milled oil it is practically impossible to have theabutting surfaces perfectly or exactly flat and smooth. Instead, therewill always be one or more high pointson the abutting surfaces. Byvirtue of the fact that the laminations are all rigid with each otherthe variations or changes in the magnetic flux soon cause the laminatedcore to vibrate as an entire unit. The momentum developed by the largelaminated core vibrating as a unit and pounding Y on-the high points onthe abutting surfaces causes the upper laminated core to act like ahammer. This hammering on the high point or points produces theobjectionable noise.

In the improved construction, however, each lamination can vibrateindependently of all of the others due to the changes in the magneticflux, but as each lamination is relatively small in weight the momentumof each lamination will likewise be small. In this manner, although thelaminations will vibrate they will not necessarily vibrate in unison andeach lamination does not have the momentum present to cause the oundingon the high point of the milled surface. Consequently, the noisegenerated by each inde pendent lamination vibrating against the surfaceis negligible and the sum or integral of the noises produced by all ofthe laminations is also practically negligible and at least is notobjectionable. A feature of the improved construction resides in thefact that not only is the noise eliminated but that it is not necessaryto go to the expense and trouble of milling off the abutting surfacesbetween the upper and lower cores. The edges of the laminations may beleft in the same condition as that in which they were originallyassembled and by virtue of the fact that the laminations are looseopposed laminations will accommodate themselves to each other and keepthe magnetic leakage between the two laminated cores at a minimum.

The theory of the short circuited coils in the lower or primary windingis as follows: After the secondary winding 32 as shown in Fig. 2 ismoved from left to ri ht some of the magnetic flux created by theprimary winding enters the secondary winding inducing currents therein.These currents will develop a magnetic flux which may be considered as aback magnetic flux which works in opposition to the flux created by thepri-- mary winding 22. The effect of the back flux is to crowd the fluxgenerated by the primary winding 22 toward the right of the primary coilso that it will passto the right of the right hand side of the secondarycoil. Because of this crowding of the flux a curve representing themagnitudes of voltages or currents induced in the secondary coil will bequite peaked instead of conforming generally to a true sine curve. Inthe improved construction as the flux generated by the primary winding22 is shifted or crowded over it will cut across the bars 35 and 36inducing currents in these bars which in turn set up a counter magneticflux in opposition to the shifting or crowding. This will counteract theeffect of the back magnetic flux developed by the secondary winding 32so that as the secondary winding is shifted over from no-load positionto a loaded position the curve representative of the magnitudes of thevoltages or currents induced therein will more nearly conform to a truesine curve having the attendant advantages.

From the above described construction it will be appreciated that anovel and advantageous laminated construction is provided which isadapted to be used in a magnetic circuit and which when placed incontact with another member in the magnetic circuit will accommodateitself thereto and produce the minimum amount of noise if any noisewhatsoever. Furthermore, an improved form of voltage regulator isprovided in which currents induced in the secondary winding will morenearlyconform to the characteristics of the currents impressed in theprimary winding.-

Various changes may be made in the details of construction withoutdeparting from the spirit or scope of the invention as defined by theappended claims.

I claim:

1. In a magnetic circuit energized by either an alternating or apulsating direct current,

two engaged opposed members adapted to be moved relatively to eachother, at least one of said members being formed of laminations whichare movable relatively to each other so that the laminations may vibrateindependently, the edges of the laminations being in engagement with theother member.

2. In a magnetic circuit energized by either an alternating or apulsating direct current, two engaged opposed members adapted to bemoved relatively to each other, both of said members being formed oflaminations which are movable relatively to each other so that thelaminations may vibrate under the influence of changes in the magneticflux independently of each other, the laminations of the members beingso arranged as to be in edge to edge relation.

3. In a magnetic circuit adapted to be energized by either analternating current or a pulsating direct current, two members adaptedto engage each other, the engaging surfaces being substantially fi'at,one of the members being laminated with its flat surface formed by theflush edges of the laminations, said member being characterized by thefact that its laminations are loose so that they may vibrateindependently of each other.

4. In a magnetic circuit adapted to be energized by either analternating current or a pulsating direct current, two members adaptedto engage each other the engaging surfaces being substantially flat,both of said members being laminated with their flat surfaces formed bythe flush edges of the laminations, said members being characterized bythe fact that their laminations are'loose so that they may vibrateindependently of each other.

5. In a magnetic circuit adapted to be energized by either analternating current or a pulsating direct current, two members adaptedto engage each other the engaging surfaces being substantially flat, oneof the members being laminated with the planes of its laminationsarranged parallel to the path of the magnetic flux, said member havingits flat surface formed by the flush edges of the laminations, and beingcharacterized by the fact that its laminations are loose so that theymay vibrate independently of each ot er.

6. In a magnetic circuit adapted to be energized by either analternating current or a pulsating direct current, two members adaptedto engage each other, said members presenting complementary engagingsurfaces, one of themembers being laminated with its engaging surfaceformed by the edges of the laminations, said member being character izedby the fact that its laminations are loose so that they may beinfluenced by the magnetic flux independently of each other.

7. In a magnetic circuit adapted to be en ergized by either analternating current or a pulsating direct current, two members adaptedto engage each other, the engaging surfaces being substantially fiat,one of the members being laminated with the edges of the laminationscooperating to produce the surface, and means for holding thelaminations in association in such a manner that the laminations areloose and may vibrate indeergized by either an alternating current or apulsating direct current, two members adapted to engage each other, theengaging surfaces being substantially flat, one of the members beinglaminated with the edges of the laminations cooperating to produce thesurface, and means for holding the laminations in association engagingthe" outer sides of the outermost laminations in such a manner as toleave the laminations loose between the holding means and thus permitthem to vibrate independently of each other.

9. In a magnetic circuit adapted to be energized by either analternating current or a pulsating direct current, two members adaptedto engage each other, the engaging surfaces being substantially flat,both of the members being laminated with the edges of the laminationscooperating to produce the surface, and means for holding the lamina--tions ofeach member in association in such a manner that the laminationsare loose and may vibrate independently of each other.

10. In a magnetic circuit adapted tobe energized by either analternating current or a pulsating direct current, two members adaptedto engage each other, the engaging surfaces being substantially fiat,both of the members being laminated with the edges of the laminationscooperating to produce the surface, and means for holding thelaminations of each member in association engaging the outer sides ofthe outermost laminations in such a manner that the laminations will beloose and thus may vibrate independently of each other.

In testimony whereof I have signed my name to this specification.

RALPH E. STEWART.

